1. Field of the Invention
This invention relates to a spark timing control device for use in an internal combustion engine, which device utilizes a vacuum for obtaining a spark advance, and more particularly to a spark timing control device which permits spark-timing control even during engine braking and starting of an automobile.
2. Description of the Prior Art
A prior art vacuum advance control mechanism for use in an internal combustion engine is directly connected to a specific port on the side of an internal combustion engine. The spark timing is advanced in response to a given level of a vacuum fed to the vacuum advance control mechanism. However, adjustment of the given level of a vacuum dictates modification of a vacuum advance control mechanism, and in addition, difficulty is confronted with modification of a spark timing control mechanism.
Furthermore, a prior art spark timing control device is designed to control spark timing, when a throttle valve is at its idling opening, as well as when the throttle valve assumes an opening larger than the idling opening, although the above spark timing control device is not intended to control spark timing during engine braking and starting of an automobile. This results in an increase in the amount of harmful constituents in the exhaust gases, as well as fuel consumption.